Free/Libre Hybrid Mobile App Framework?
Ionic and React Native are famous hybrid app frameworks. They are qualified as "open source" as their license is MIT but I'm not sure if they are fully free. They are not listed on the Free Software Directory. I hardly find any discussion about them within the free software community.
There are two "MIT" licenses: X11 and Expat. Both are free software licenses. See https://www.gnu.org/licenses/license-list.html#X11License and https://www.gnu.org/licenses/license-list.html#Expat
There's actually more than that if you look at all of the variants that MIT has used over the years, in the Old Style area: https://fedoraproject.org/wiki/Licensing:MIT
So there really isn't one "MIT" license and the very name "the MIT license" is ambiguous.